Conventional rotor core assemblies in electric motors include components, such as laminations and end plates, that must be securely fastened together to prevent damage to the rotor and to the motor during rotation. If the components loosen, the core may become unbalanced, causing the motor to stop or vibrate. And if the motor is to be used for high-speed applications, e.g., speeds greater than about 7000 rpm, it becomes even more critical that the components are securely fastened together if the motor fails.
Conventional high-speed rotor cores are manufactured using adhesives because adhesives tend to form a secure bond between the components that lasts the life of the motor. Rivets do not have sufficient clamping force, and threaded bolts may loosen over the life of the motor. Additionally, bolts made of stainless steel are known to expand at a much greater rate than steel bolts, so their use is disfavored in motors because they may allow the laminations to loosen. Thus, mechanical fasteners in rotor cores are typically avoided in high-speed applications to minimize loosening of components. Moreover, such mechanical fasteners are known to negatively impact operation of the motor, as by disturbing the magnetic flux path and causing unwanted eddy currents.
The process of making a rotor core using adhesive as a fastener is relatively expensive. For example, the adhesive must be cured for more than an hour, which makes the process very time-consuming. Accordingly, a rotor core and motor that solves the shortcomings of the prior art is needed.